Carbonate-catalyzed polycrystalline diamond elements, methods of manufacturing the same,  and applications therefor

ABSTRACT

In an embodiment, a polycrystalline diamond compact includes a substrate and a preformed polycrystalline diamond table bonded to the substrate. The table includes bonded diamond grains defining interstitial regions. The table includes an upper surface, a back surface bonded to the substrate, and at least one lateral surface extending therebetween. The table includes a first region extending inwardly from the upper surface and the lateral surface. The first region exhibits a first interstitial region concentration and includes at least one interstitial constituent disposed therein, which may be present in at least a residual amount and includes at least one metal carbonate and/or at least one metal oxide. The table includes a second bonding region adjacent to the substrate that extends inwardly from the back surface. The second bonding region exhibits a second interstitial region concentration that is greater than the first interstitial region concentration and includes a metallic infiltrant therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/552,052 filed on 18 Jul. 2012, which claims priority to U.S.Provisional Application No. 61/509,823 filed on 20 Jul. 2011, thedisclosure of each of which is incorporated herein, in its entirety, bythis reference.

BACKGROUND

Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilizedin a variety of mechanical applications. For example, PDCs are used indrilling tools (e.g., cutting elements, gage trimmers, etc.), machiningequipment, bearing apparatuses, wire-drawing machinery, and in othermechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller-cone drill bits and fixed-cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly known as a diamond table. The diamond table is formed andbonded to a substrate using a high-pressure/high-temperature (“HPHT”)process. The PDC cutting element may also be brazed directly into apreformed pocket, socket, or other receptacle formed in a bit body. Thesubstrate may often be brazed or otherwise joined to an attachmentmember, such as a cylindrical backing. A rotary drill bit typicallyincludes a number of PDC cutting elements affixed to the bit body. It isalso known that a stud carrying the PDC may be used as a PDC cuttingelement when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container with a volume of diamond particles positionedon a surface of the cemented carbide substrate. A number of suchcontainers may be loaded into an HPHT press. The substrate(s) and volumeof diamond particles are then processed under HPHT conditions in thepresence of a catalyst material that causes the diamond particles tobond to one another to form a matrix of bonded diamond grains defining apolycrystalline diamond (“PCD”) table. The catalyst material is often ametal-solvent catalyst (e.g., cobalt, nickel, iron, or alloys thereof)that is used for promoting intergrowth of the diamond particles.

In one conventional approach, a constituent of the cemented carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a metal-solventcatalyst to promote intergrowth between the diamond particles, whichresults in the formation of a matrix of bonded diamond grains havingdiamond-to-diamond bonding therebetween, with interstitial regionsbetween the bonded diamond grains being occupied by the metal-solventcatalyst.

The presence of the metal-solvent catalyst in the PCD table is believedto reduce the thermal stability of the PCD table at elevatedtemperatures. For example, chipping or cracking of the PCD table duringdrilling or cutting operations is believed to be due to the presence ofthe metal-solvent catalyst, which consequently can degrade themechanical properties of the PCD table or cause failure. Additionally,some of the diamond grains can undergo a chemical breakdown orback-conversion to graphite via interaction with the solvent catalyst.At elevated high temperatures, portions of diamond grains may transformto carbon monoxide, carbon dioxide, graphite, or combinations thereof,causing degradation of the mechanical properties of the PCD table.

Despite the availability of a number of different PDCs, manufacturersand users of PDCs continue to seek PDCs that exhibit improved toughness,wear resistance, and thermal stability.

SUMMARY

Embodiments of the invention relate to PDCs including a PCD tablesintered using at least one carbonate catalyst material having a bondingregion with a relatively high interstitial region concentration thatenables effective infiltration therein with a metallic infiltrant forbonding to a substrate, and methods of fabricating such PDCs. The PDCsdisclosed herein may be used in a variety of applications, such asrotary drill bits, bearing apparatuses, wire-drawing dies, machiningequipment, and other articles and apparatuses.

In an embodiment, a PDC includes a substrate and a preformed PCD tablebonded to the substrate. The preformed PCD table includes bonded diamondgrains defining a plurality of interstitial regions. The preformed PCDtable further includes an upper surface, a back surface bonded to thesubstrate, and at least one lateral surface extending between the uppersurface and the back surface. The preformed PCD table additionallyincludes a first region extending inwardly from the upper surface andthe at least one lateral surface. The first region exhibits a firstinterstitial region concentration and includes at least one interstitialconstituent disposed in at least a portion of the interstitial regions.The at least one interstitial constituent may be present in at least aresidual amount. The at least one interstitial constituent includes atleast one metal carbonate and/or at least one metal oxide. The preformedPCD table also includes a second bonding region adjacent to thesubstrate and extending inwardly from the back surface. The secondbonding region exhibits a second interstitial region concentration thatis greater than the first interstitial region concentration and includesa metallic infiltrant therein disposed in at least a portion of theinterstitial regions.

In an embodiment, a method of fabricating a PDC is disclosed. The methodincludes assembling a preformed PCD table with a substrate. Thepreformed PCD table includes bonded diamond grains defining a pluralityof interstitial regions. The preformed PCD table further includes anupper surface, a back surface bonded to the substrate, and at least onelateral surface extending between the upper surface and the backsurface. The preformed PCD table additionally includes a first regionextending inwardly from the upper surface and the at least one lateralsurface. The first region includes at least one interstitial constituentdisposed in at least a portion of the interstitial regions. The at leastone interstitial constituent may be present in at least a residualamount. The at least one interstitial constituent includes at least onemetal carbonate and/or at least one metal oxide. The preformed PCD tablealso includes a second bonding region adjacent to the substrate andextending inwardly from the back surface. The second bonding regionexhibits an interstitial region concentration that is greater than thatof the first region. The method further includes infiltrating at least aportion of the interstitial regions of the second bonding region of thePCD table with a metallic infiltrant effective to bond the PCD table tothe substrate

Other embodiments include applications utilizing the disclosed PDCs invarious articles and apparatuses, such as rotary drill bits, bearingapparatuses, wire-drawing dies, machining equipment, and other articlesand apparatuses.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical or similar elements orfeatures in different views or embodiments shown in the drawings.

FIG. 1A is a cross-sectional view of an embodiment of a PDC.

FIG. 1B is an isometric view of the PDC shown in FIG. 1A.

FIG. 1C is a cross-sectional view of another embodiment of a PDCincluding a PCD table that has been depleted of at least oneinterstitial constituent.

FIG. 1D is a cross-sectional view of another embodiment of a PDC havinga PCD table leached to a selected depth.

FIG. 2 is a cross-sectional view of another embodiment of a PDCincluding a preformed PCD table brazed to a substrate.

FIGS. 3A-3F are cross-sectional views at different stages during amethod of manufacturing the PDC shown in FIG. 1A according to anembodiment.

FIG. 4A is a graph of magnesium content profile measured in themagnesium-carbonate-catalyzed PCD tables of Working Examples 1-3.

FIG. 4B is a graph of metal content profile measured in themagnesium-carbonate-catalyzed PCD tables of Working Example 4.

FIG. 5 is a graph of profile of magnesium and cobalt content measured inthe magnesium-carbonate-catalyzed PCD tables of Working Examples 5 and6.

FIG. 6A is a backscattered electron scanning electron microscope (“SEM”)image of one of the magnesium-carbonate-catalyzed PCD tables of WorkingExample 8 at 750 times magnification.

FIGS. 6B-6E are photographs of wear scars on one of the PDCs of WorkingExample 8 and a conventional cobalt-sintered PDC after cutting a graniteworkpiece.

FIG. 6F is a statistical comparison of wear volumes between the PDCs ofWorking Example 8 and conventional cobalt-sintered PDCs after removing15,400 cm³ of rock on the wet VTL test.

FIG. 6G is a statistical comparison of thermal stability between thePDCs of Working Example 8 and the conventional cobalt-sintered PDCs.

FIG. 6H is the statistical comparison of rupture strength between WC-13weight % Co, the conventional cobalt-sintered PDC discs, and the PDCs ofWorking Example 8.

FIG. 7A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 7B is a top elevation view of the rotary drill bit shown in FIG.7A.

FIG. 8 is an isometric cut-away view of an embodiment of thethrust-bearing apparatus, which may utilize any of the disclosed PDCembodiments as bearing elements.

FIG. 9 is an isometric cut-away view of an embodiment of a radialbearing apparatus, which may utilize any of the disclosed PDCembodiments as bearing elements.

DETAILED DESCRIPTION

Embodiments of the invention relate to PDCs including a PCD tablesintered using at least one carbonate catalyst material having a bondingregion with a relatively high interstitial region concentration thatenables effective infiltration therein with a metallic infiltrant forbonding to a substrate, and methods of fabricating such PDCs. The PDCsdisclosed herein may be used in a variety of applications, such asrotary drill bits, bearing apparatuses, wire-drawing dies, machiningequipment, and other articles and apparatuses.

FIGS. 1A and 1B are cross-sectional and isometric views, respectively,of an embodiment of a PDC 100 including a preformed carbonate-catalyzedPCD table 102 that was sintered using at least one carbonate catalystmaterial. The PCD table 102 includes a working upper surface 104, agenerally opposing interfacial back surface 106, and at least onelateral surface 107 extending therebetween. It is noted that at least aportion of the at least one lateral surface 107 may also function as aworking surface that contacts a subterranean formation during drilling.In the illustrated embodiment, the preformed PCD table 102 also includesan optional chamfer 109. The chamfer 109 extends between the uppersurface 104 and the at least one lateral surface 107.

The back surface 106 of the PCD table 102 is bonded to a substrate 108.The substrate 108 may include, without limitation, cemented carbides,such as tungsten carbide, titanium carbide, chromium carbide, niobiumcarbide, tantalum carbide, vanadium carbide, or combinations thereofcemented with iron, nickel, cobalt, or alloys thereof. In an embodiment,the substrate 108 comprises cobalt-cemented tungsten carbide. Althoughthe back surface 106 of the PCD table 102 is depicted in FIG. 1A asbeing substantially planar, in other embodiments, the back surface 106may exhibit a selected nonplanar topography and the substrate 108 mayexhibit a correspondingly configured interfacial surface or otherselected interfacial surface.

The PCD table 102 includes a plurality of directly bonded-togetherdiamond grains having diamond-to-diamond bonding (e.g., sp³ bonding)therebetween. The plurality of bonded diamond grains defines a pluralityof interstitial regions. As shown in FIG. 1A, the PCD table 102 includesa first region 112 having a first interstitial region concentration ofinterstitial regions and a second bonding region 114 adjacent to thesubstrate 108 and having a second interstitial region concentration ofinterstitial regions that is greater than that of the first interstitialregion concentration. For example, each of the first and secondinterstitial region concentration may be characterized by a volume ofinterstitial regions as a percentage of a selected volume orcross-sectional area of interstitial regions as a percentage of aselected cross-sectional area. The first and second interstitial regionconcentrations may be measured by volumetric, area fraction, x-raytomography, or other methods. U.S. patent application Ser. No.12/942,524 filed on Nov. 9, 2010 discloses one suitable computedtomography system for determining interstitial region concentration andis incorporated herein, in its entirety, by this reference. For example,the second interstitial region concentration may be about 1.2 to about1.5 times the first interstitial region concentration, at least 2 ormore times the first interstitial region concentration, about 2 to about4 times the first interstitial region concentration, about 3 to about 5times the first interstitial region concentration. The first region 112and the bonding region 114 may include at least one interstitialconstituent disposed in at least a portion of the interstitial regionsthereof. The at least one interstitial constituent includes at least onemetal carbonate and/or at least one metal oxide (e.g., formed byconversion of the at least one metal carbonate after formation of thePCD table 102 and/or as a sintering by-product formed during HPHTsintering of diamond particles to form the diamond-to-diamond bondingbetween the diamond grains of the PCD table 102).

The at least one interstitial constituent, including the at least onemetal carbonate and/or at least one metal oxide, may be present atand/or near the upper surface 104 of the first region 112 in an amountgreater than 0 (zero) weight % to about 5 weight %, about 2 weight % toabout 4 weight %, about 1 weight % to about 2 weight %, about 1 weight %to about 3 weight %, about 2 weight % to about 3 weight %, or about 1.5weight % to about 2.5 weight %. The at least one interstitialconstituent, including the at least one metal carbonate and/or at leastone metal oxide, may be present at and/or near the back surface 106 ofthe bonding region 114 in an amount greater than zero weight % to about1.5 weight %, about 0.5 weight % to about 1.5 weight %, about 0.3 weight% to about 0.7 weight %, about 0.5 weight % to about 0.8 weight %, about0.6 weight % to about 1 weight %, or about 0.5 weight % to about 0.8weight %. The amount of the at least one interstitial constituent may bemeasured using energy dispersive spectroscopy (“EDS”) or Rietveld x-raydiffraction (“XRD”) analysis.

It should be noted that the composition of the first region 112 maychange with increasing distance toward the bonding region 114. Forexample, the concentration of the at least one interstitial constituentmay decrease with increasing distance toward the bonding region 114.

The at least one metal carbonate present in the PCD table 102 may beselected from one or more alkali metal carbonates (e.g., one or morecarbonates of Li, Na, and K), one or more alkaline earth metalcarbonates (e.g., one or more carbonates of Be, Mg, Ca, Sr, and Ba), andany combination of the foregoing carbonates. The at least one metaloxide present in the PCD table 102 may be selected from one or morealkali metal oxides (e.g., one or more oxides of Li, Na, and K), one ormore alkaline earth metal oxides (e.g., one or more carbonates of Be,Mg, Ca, Sr, and Ba), and any combination of the foregoing oxides.

In the illustrated embodiment, the first region 112 of the PCD table 102extends laterally along the upper surface 104 and the optional chamfer109. The depth “d” to which the first region 112 extends inwardly fromthe upper surface 104 may be about 50 μm to about 1000 μm, about 200 μmto about 500 μm, about 300 μm to about 450 μm, about 500 μm to about 700μm, about 1000 μm to about 2000 μm, about 700 μm to about 1000 μm, about0.1 mm to about 0.5 mm, about 0.25 mm to about 0.45 mm, or about 0.3 mmto about 0.4 mm. In some embodiments, the first region 112 may extendbelow the chamfer 109 as illustrated, while in other embodiments, thefirst region 112 may not extend past the bottom of the chamfer 109.

The bonding region 114 may be disposed between the first region 112 andthe substrate 108, and extends along at least the back surface 106 ofthe PCD table 102. The bonding region 114 extends inwardly from the backsurface 106 to a selected depth “D,” which may be less than the depth“d,” as shown in FIG. 1A. At least a portion of the relatively highlyconcentrated interstitial regions of the bonding region 114 may includea metallic infiltrant disposed therein that is infiltrated and providedfrom the substrate 108 or another source such as a braze alloy. Forexample, the metallic infiltrant may comprise iron, nickel, cobalt, oralloys thereof. As a further example, when the substrate 108 is acobalt-cemented tungsten carbide substrate, the metallic infiltrant maycomprise cobalt that infiltrates into the bonding region 114 of the PCDtable 102 during bonding of the PCD table 102 to the substrate 108 in anHPHT process.

In some embodiments, the infiltration may extend throughout the bondingregion 114 and at least some of the first region 112 depending upon theextent to which the metallic infiltrant infiltrates. However, more ofthe metallic infiltrant occupies the bonding region 114 due to theincreased interstitial region concentration compared to the first region112.

FIG. 1C is a cross-sectional view of another embodiment of a PDC 100′including a PCD table 102′ that has been depleted of the at least oneinterstitial constituent substantially therethrough. As shown in FIG.1C, the PCD table 102′ includes a bonding region 114′ including ametallic infiltrant disposed therein that is infiltrated from thesubstrate 108 or other source and a first region 112′ that has beendepleted of the at least one interstitial constituent prior toattachment to the substrate 108. The PCD table 102 may be formed byleaching a preformed carbonate-catalyzed PCD table. For example, theregions 112′ and 114′ of PCD table 102′ may include a residual amount ofthe at least one interstitial constituent and/or one or more leachingby-products disposed in at least a portion of the interstitial regionsthereof due to the regions being formed by leaching and at leastpartially removing the at least one interstitial constituent therefrom.For example, the at least one interstitial constituent may be present inthe regions 112′ and 114′ of the PCD table 102′ in a residual amount ofabout 0.05 weight % to about 1.50 weight %, about 0.8 weight % to about1.50 weight %, or about 0.9 weight % to about 1.2 weight % of the PCDtable 102. The one or more leaching by-products may include one or morechlorides of Be, Mg, Ca, Sr, Ba, Li, Na, and K; one or more fluorides ofBe, Mg, Ca, Sr, Ba, Li, Na, and K; or any combination of the foregoingsalts.

Similar to the bonding region 114 of PDC 100, the bonding region 114′ ofPDC 100′ extends inwardly from the back surface 106 to a selected depth“D”. For example, the depth “D” to which the bonding region 114′ extendsinwardly from the back surface 106 may be about 50 μm to about 1000 μm,about 200 μm to about 500 μm, about 300 μm to about 450 μm, about 500 μmto about 700 μm, or about 700 μm to about 1000 μm.

Depending on the extent of infiltration, the bonding region 114′ mayextend to or proximate to the upper surface 104 of the first region 112′in FIG. 1C. Referring to FIG. 1D, in yet a further embodiment when themetallic infiltrant deeply infiltrates into the preformed PCD table,following infiltration, the metallic infiltrant may be acid leached to aselected depth “d” measured from at least one of the upper surface 104,the chamfer 109, or the at least one lateral surface 107 to form aleached region 115 that is depleted of the metallic infiltrant. Forexample, the depth “d” to which the first region 112′ extends may beabout 50 μm to about 1000 μm, about 200 μm to about 500 μm, about 300 μmto about 450 μm, about 500 μm to about 700 μm, about 1000 μm to about2000 μm, or about 700 μm to about 1000 μm. For example, the leachedregion 115 may generally contour one or more of the upper surface 104,the chamfer 109, or the at least one lateral surface 107. The leachedregion 115 may extend along a selected length of the at least onelateral surface 107. A residual amount of the metallic infiltrant may bepresent in the leached region 115 even after leaching. For example, themetallic infiltrant may comprise about 0.8 weight % to about 1.50 weight%, or about 0.9 weight % to about 1.2 weight % of the PCD table.

FIG. 2 is a cross-sectional view of an embodiment of a PDC 200 in whicha preformed carbonate-catalyzed PCD table 102 (as shown in FIG. 1A) isbrazed to the substrate 108. At least a portion of the interstitialregions of the bonding region 114 may include braze alloy disposedtherein that has been infiltrated and provided from the braze alloylayer 216. In some embodiments, a thickness “t” of the braze alloy layer216 may be tailored to at least improve (e.g., maximize) joint strengthbetween the substrate 108 and the PCD table 102. For example, thethickness “t” may be about 0.0010 inch to about 0.050 inch, such asabout 0.0050 inch to about 0.050 inch or about 0.010 inch to about 0.020inch. Depending upon the extent of infiltration of the braze alloy, thebraze alloy layer 216 may not be present because substantially all ofthe material thereof may have infiltrated into the PCD table 102 and ispresent substantially only in the bonding region 114. In someembodiments, the braze alloy may negligibly infiltrate into the bondingregion 114.

Suitable braze alloys for the braze alloy layer 216 include gold,silver, copper, or titanium alloys. For example, suitable braze alloysfor the braze alloy layer 216 may include gold-tantalum alloys orsilver-copper-titanium alloys. In an embodiment, the braze alloy for thebraze alloy layer 216 may be an active braze alloy. For example, onesuitable active braze alloy for the braze alloy layer 216 is an alloy ofabout 4.5 weight % titanium, about 26.7 weight % copper, and about 68.8weight % silver, otherwise known as TICUSIL®, which is currentlycommercially available from Wesgo Metals, Hayward, Calif. Yet anothersuitable titanium active braze alloy for the braze alloy layer 216 isCopper ABA™ braze alloy, which has a composition of about 92.75 weight %copper, about 3.0 weight % silicon, about 2.25 weight % titanium, and2.0 weight % aluminum. In a further embodiment, a braze alloy for thebraze alloy layer 216 may comprise an alloy of about 25 weight % gold,about 37 weight % copper, about 10 weight % nickel, about 15 weight %palladium, and about 13 weight % manganese, otherwise known asPALNICUROM® 10, which is also currently commercially available fromWesgo Metals, Hayward, Calif. Another suitable braze alloy may includeabout 92.3 weight % nickel, about 3.2 weight % boron, and about 4.5weight % silicon. Yet another suitable braze alloy may include about92.8 weight % nickel, about 1.6 weight % boron, and about 5.6 weight %silicon.

Although the PDCs 100, 100′, and 200 shown in FIGS. 1A-2 are illustratedas being cylindrical, the PDCs disclosed herein may exhibit otherselected configurations. For example, the PDCs may exhibit arectangular, triangular, elliptical, or other selected configuration.

FIGS. 3A-3F are cross-sectional views at different stages during amethod of manufacturing the PDC 100 shown in FIG. 1A according to anembodiment. FIG. 3A is a cross-sectional view of an embodiment of a PCDprecursor assembly 300 for forming two carbonate catalyzed PCD tables.At least one carbonate catalyst material 304 (e.g., a powder or disk) isdisposed between first and second regions 302 and 305 each including aplurality of diamond particles, thereby forming the PCD precursorassembly 300. The PCD precursor assembly 300 may be subjected to an HPHTprocess to partially or completely melt the carbonate catalyst material304 and sinter the plurality of diamond particle regions 302 and 305 toform a second PCD precursor assembly 320 as shown in FIG. 3B. As will beapparent from the description further below, placement of the carbonatecatalyst material 304 between the plurality of diamond particle regions302 and 305 not only catalyzes the growth of additional diamond betweenthe diamond particles during HPHT processing, but also provides for theformation of regions 312 and 312′ of PCD tables 322 and 322′ so formed(see FIGS. 3B and 3C) exhibiting increased diamond-to-diamond bondingbetween the diamond grains. The presence of the carbonate catalystmaterial 304 between the plurality of diamond particle regions 302 and305 during HPHT processing also provides for the formation of bondingregions 314 and 314′ in the PCD tables 322 and 322′ (see FIGS. 3B and3C) exhibiting an increased interstitial porosity concentration ascompared to the regions 312 and 312′. The bonding regions 314 and 314′shown FIGS. 3B and 3C having a relatively greater interstitial porosityfacilitate infiltration of metallic infiltrant into the interstitialregions between the diamond grains of a carbonate-catalyzed PCD tableduring bonding of the PCD table to a substrate.

The plurality of diamond particles of the first and second regions 302and 305 (shown in FIG. 3A) may be chosen from natural diamond, syntheticdiamond, or combinations thereof. The plurality of diamond particles 302and 305 (shown in FIG. 3A) may also exhibit one or more selected sizes.The one or more selected sizes may be determined, for example, bypassing the diamond particles through one or more sizing sieves or byany other method. In an embodiment, the plurality of diamond particlesmay include a relatively larger size and at least one relatively smallersize. As used herein, the phrases “relatively larger” and “relativelysmaller” refer to particle sizes determined by any suitable method,which differ by at least a factor of two (e.g., 40 μm and 20 μm). Moreparticularly, in various embodiments, the plurality of diamond particlesmay include a portion exhibiting a relatively larger size (e.g., 100 μm,90 μm, 80 μm, 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10μm, 8 μm) and another portion exhibiting at least one relatively smallersize (e.g., 30 μm, 20 μm, 10 μm, 15 μm, 12 μm, 10 μm, 8 μm, 4 μm, 2 μm,1 μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In anembodiment, the plurality of diamond particles may include a portionexhibiting a relatively larger size between about 40 μm and about 15 μmand another portion exhibiting a relatively smaller size between about12 μm and 2 μm. Of course, the plurality of diamond particles may alsoinclude three or more different sizes (e.g., one relatively larger sizeand two or more relatively smaller sizes) without limitation.

In some embodiments, each of the plurality of diamond particles 302 and305 may include two or more layers exhibiting different compositionsand/or different average diamond particle sizes. For example, a firstlayer may be located adjacent to the at least one carbonate catalystmaterial 304 and exhibit a first diamond particle size, while a secondlayer may be located remote from the at least one carbonate catalystmaterial 304 and exhibit a second average diamond particle size that isless than that of the first average diamond particle size. For example,the second average diamond particle size may be about 90% to about 98%(e.g., about 90 to about 95%) of the first diamond particle size. Inanother embodiment, the second average diamond particle size may begreater than that of the first average diamond particle size. Forexample, the first average diamond particle size may be about 90% toabout 98% (e.g., about 90 to about 95%) of the second diamond particlesize.

As an alternative to or in addition to the first and second layersexhibiting different diamond particles sizes, in an embodiment, thecomposition of the first layer may be different than that of the secondlayer. The first layer may include about 15 weight % or less of atungsten-containing material (e.g., tungsten and/or tungsten carbide)mixed with the diamond particles, while the second layer may besubstantially free of tungsten. For example, the tungsten-containingmaterial may be present in the first layer in an amount of about 1weight % to about 10 weight %, about 5 weight % to about 10 weight %, orabout 10 weight %.

The carbonate catalyst material 304 (shown in FIG. 3A) may include oneor more alkali metal carbonates (e.g., one or more carbonates of Li, Na,and K), one or more alkaline earth metal carbonates (e.g., one or morecarbonates of Be, Mg, Ca, Sr, and Ba), or any combination of theforegoing carbonates. For example, the at least one carbonate catalystmaterial 304 may be formed by pressing fine powder of the at least onecarbonate catalyst material. Such fine powder may be commerciallyavailable from Causmag International. According to an embodiment, the atleast one carbonate catalyst material 304 may include a first alkalineearth metal carbonate and at least a second alkaline earth metalcarbonate present in selected proportions at or near a eutecticcomposition for the chemical system defined by the first and at least asecond alkaline earth metal carbonates. In an embodiment, the firstalkaline earth metal carbonate may be selected from a Group II carbonate(e.g., a carbonate of Be, Mg, Ca, Sr, Ba, or Ra) and the at least asecond alkaline earth metal carbonate may be selected from one or moreGroup II carbonates that are different than that of the first alkalineearth metal carbonate. For example, the first alkaline earth metalcarbonate and the at least a second alkaline earth metal carbonate mayform a binary or greater chemical system that exhibits a eutectic point,and the first alkaline earth metal carbonate and the at least a secondalkaline earth metal carbonate may form a eutectic, hypereutectic, orhypoeutectic composition.

According to an embodiment, the at least one carbonate catalyst materialmay comprise magnesium carbonate and a second carbonate catalystmaterial such as calcium carbonate. In an embodiment, the magnesiumcarbonate and calcium carbonate may be present in selected proportionsat or near a binary eutectic composition (e.g., a eutectic composition,a hypereutectic composition, or a hypoeutectic composition) for themagnesium carbonate-calcium carbonate chemical system.

In order to efficiently sinter the plurality of diamond particles 302and 305 to form the PCD tables 322 and 322′, the PCD precursor assembly300 may be enclosed in a pressure transmitting medium, such as arefractory metal can, graphite structure, pyrophyllite, combinationsthereof, or other suitable pressure transmitting structure to form acell assembly. In some embodiments, the mixture may be sealed in a canassembly. Examples of suitable gasket materials and cell structures foruse in manufacturing PCD are disclosed in U.S. Pat. No. 6,338,754 andU.S. patent application Ser. No. 11/545,929, each of which isincorporated herein, in its entirety, by this reference. Another exampleof a suitable pressure transmitting material is pyrophyllite, which iscommercially available from Wonderstone Ltd. of South Africa. The PCDprecursor assembly 300, including the plurality of diamond particles 302and 305 and the carbonate catalyst material 304, is subjected to an HPHTprocess using an ultra-high pressure press (e.g., a cubic press) at atemperature of at least about 1400° C. and a pressure in the pressuretransmitting medium of at least about 7.5 GPa for a time sufficient tosinter the diamond particles together and form the PCD tables 322 and322′ comprising directly bonded-together diamond grains. Further detailsabout HPHT processing techniques that may be used to practice theembodiments disclosed herein are disclosed in U.S. Pat. No. 7,866,418,which is incorporated herein, in its entirety, by reference. Forexample, the temperature may be about 1700° C. to about 2700° C., about2000° C. to about 2400° C., about 2200° C. to about 2400° C. or about2300° C. to about 2450° C. and the pressure may be about 7.5 GPa toabout 15 GPa, about 9 GPa to about 12 GPa, about 8 GPa to about 10 GPa,or about 10 GPa to about 12.5 GPa.

The pressure values employed in the HPHT processes disclosed hereinrefer to the pressure in the pressure transmitting medium at roomtemperature (e.g., about 25° C., or slightly above due to compressive(friction) heating) with application of pressure using an ultra-highpressure press and not the pressure applied to the exterior of the cellassembly. The actual pressure in the pressure transmitting medium atsintering temperature may be higher. The ultra-high pressure press maybe calibrated at room temperature by embedding at least one calibrationmaterial that changes structure at a known pressure, such as PbTe,thallium, barium, or bismuth in the pressure transmitting medium.Further, optionally, a change in resistance may be measured across theat least one calibration material due to a phase change thereof. Forexample, PbTe exhibits a phase change at room temperature at about 6.0GPa and bismuth exhibits a phase change at room temperature at about 7.7GPa. Examples of suitable pressure calibration techniques are disclosedin G. Rousse, S. Klotz, A. M. Saitta, J. Rodriguez-Carvajal, M. I.McMahon, B. Couzinet, and M. Mezouar, “Structure of the IntermediatePhase of PbTe at High Pressure,” Physical Review B: Condensed Matter andMaterials Physics, 71, 224116 (2005) and D. L. Decker, W. A. Bassett, L.Merrill, H. T. Hall, and J. D. Barnett, “High-Pressure Calibration: ACritical Review,” J. Phys. Chem. Ref. Data, 1, 3 (1972).

Referring to both FIGS. 3A and 3B, during the HPHT process, thecarbonate catalyst material 304 may at least partially or completelymelt and infiltrate into the plurality of diamond particle regions 302and 305 to facilitate diamond growth and sinter the plurality of diamondparticle regions 302 and 305 to form the PCD tables 322 and 322′. It isnoted that the as-sintered average diamond grain size of respective PCDtables 322 and 322′ formed after HPHT processing shown in FIG. 3B maysubstantially the same as or different from the average particle size ofthe plurality of diamond particles prior to sintering due to a varietyof different physical processes, such as grain growth, diamond particlesfracturing, nucleation and subsequent growth of new diamond crystals,carbon provided from another carbon source, or combinations of theforegoing.

The PCD tables 322/322′ exhibit respective first regions 312/312′ andbonding regions 314/314′ having relatively higher porosity concentration(as measured by any of the disclosed measurement techniques) than thefirst regions 312/312′. The PCD tables 322 and 322′ so-formed includedirectly bonded-together diamond grains exhibiting diamond-to-diamondbonding (e.g., sp³ bonding) therebetween. The plurality of bondeddiamond grains defines a plurality of interstitial regions. Most of theinterstitial regions near the carbonate catalyst material 304 areinfiltrated with the at least one carbonate catalyst material that actsas a sintering aid. As the at least one carbonate catalyst material 304infiltrates the diamond particles during HPHT processing, a gradient ofinterstitial region porosity concentration may be formed within the PCDtables 322 and 322′ that increases from surfaces 307 and 307′ towardsurfaces 309 and 309′ of the respective bonding regions 314 and 314′.The bonding region 314 has an interstitial region porosity concentrationthat is greater than the interstitial region porosity concentration ofthe region 312, and the bonding region 314′ has an interstitial regionporosity concentration that is greater than the interstitial regionporosity concentration of the region 312′. For example, the interstitialregion porosity concentration of the bonding region 314/314′ may beabout 1.2 to about 1.5 times the interstitial region porosityconcentration of the region 312/312′, at least 2 or more times theinterstitial region porosity concentration of the region 312/312′, about2 to about 4 times the interstitial region porosity concentration of theregion 312/312′, about 3 to about 5 times the interstitial regionporosity concentration of the region 312/312′.

The PCD tables 322 and 322′ includes at least one interstitialconstituent disposed in at least a portion of the interstitial regionsbetween the bonded diamond grains thereof. The at least one interstitialconstituent includes the at least one metal carbonate and/or at leastone metal oxide converted from the at least one metal carbonate. The atleast one interstitial constituent may be present at and/or near thesurface 307/307′ of the region 312/312′ in an amount greater than 0(zero) weight % to about 5 weight %, about 1 weight % to about 2 weight%, about 2 weight % to about 4 weight %, about 2 weight % to about 3weight %, about 1 weight % to about 3 weight %, or about 1.5 weight % toabout 2.5 weight %. The at least one interstitial constituent, includingthe at least one metal carbonate and/or at least one metal oxide, may bepresent at and/or near the surface 309/309′ of the bonding region314/314′ in an amount greater than 0 (zero) weight % to about 1.5 weight%, about 0.3 weight % to about 0.7 weight %, about 0.5 weight % to about1.5 weight %, about 0.4 weight % to about 0.8 weight %, about 0.6 weight% to about 1 weight %, or about 0.5 weight % to about 0.8 weight %. Theconcentration of the at least one interstitial constituent, maygradually increase with increasing distance from the bonding region 114to the first region 112.

Referring to FIG. 3C, once formed, the PCD precursor assembly 320 may beseparated by hand to form the respective PCD tables 322 and 322′. Inother embodiments, if the PCD tables 322 and 322′ are attached to eachother directly, along respective surfaces 307 and 307′. In such anembodiment, the PCD tables 322 and 322′ may be separated from the PCDprecursor assembly 320 using laser cutting, electrical dischargemachining (“EDM”), or other suitable methods. For example, U.S. patentapplication Ser. No. 13/166,007, which is incorporated herein in itsentirety by this reference, discloses various laser cutting techniquesfor cutting the PCD tables 322 and 322′ from the PCD table precursor320.

During the HPHT processing, it may be possible to cause some orsubstantially all of the at least one metal carbonate present in the PCDtables 322 and 322′ to convert to a corresponding metal oxide. On theother hand, the at least one metal carbonate may remain in the PCDtables 322 and 322′. For example, in an embodiment, when magnesiumcarbonate is employed as a metal carbonate catalyst, some orsubstantially all of the magnesium carbonate may convert to magnesiumoxide during the HPHT process. However, in any of the embodimentsdisclosed herein, the PCD tables 322 and 322′ may be heat treated toconvert some or substantially all of the at least one metal carbonatepresent in the PCD tables 322 and 322′ to a corresponding at least onemetal oxide prior to the process in which the PCD tables 322 and 322′are bonded to a substrate.

In some embodiments, heat treating the PCD tables 322 and 322′ prior tobonding to a substrate may provide for more effective infiltration ofthe porous bonding regions 314 and 314′ during bonding. Such heattreatment may result in the removal of gaseous by-products from theconversion of metal carbonates to metal oxides, such as carbon monoxideand/or carbon dioxide. The removal of these gaseous by-products maypromote bonding of the PCD tables 322 and 322′ to a metallic substrateby facilitating effective infiltration of the interstitial regionsbetween the diamond grains of the PCD tables with a metallic infiltrantwithout interference from the gaseous by-products. For example, thecarbonate catalyzed PCD tables 322 and 322′ may be heat treated atemperature of about 700° C. to about 1400° C. (e.g., about 1000° C. toabout 1300° C., or about 1100° C. to about 1200° C.) for a time (e.g.,more than an 1 hour, about 0.5 hour to about 1.5 hour, about 0.8 hour toabout 1 hour, or about 2 hours to about 5 hours) sufficient to convertat least some or at least most of the at least one metal carbonate to acorresponding at least one metal oxide, thereby releasing gaseousby-products generated during the heat treating process.

Referring back to FIG. 3C, once separated from the PCD assembly 320, insome embodiments, the carbonate catalyzed PCD tables 322 and 322′ may besubjected to a material removal process to remove at least a portion ofthe at least one interstitial constituent therefrom to form a treatedcarbonate-catalyzed PCD table 340 (see FIG. 3D) including a gradient ofporosity, with interstitial porosity concentration increasing from theregion 312, toward the bonding region 314. In some embodiments, thematerial removal process may be performed after heat treating the PCDtables 322 and 322′. In other embodiments, the material removal processmay be performed before heat treating the PCD tables 322 and 322′.

In an embodiment, the material removal may be a leaching process. Forexample, the carbonate-catalyzed PCD table 322 may be immersed in anacid (e.g., hydrochloric acid, nitric acid, hydrofluoric acid, aceticacid, or mixtures thereof) for a time sufficient to remove the at leastone interstitial constituent. As an alternative to or in addition to theforegoing acids, boiling water may also be used for leaching. Forexample, the leaching may be performed for a time ranging from a fewhours to a few days. In some embodiments, the leaching process may bemore effective when performed after heating treating in which the metalcarbonate (e.g., magnesium carbonate) is converted to a metal oxide(e.g., magnesium oxide). The amount of material removed from the tworegions 312 and 314 may vary due to the differences in interstitialregion concentration within each of the regions.

In some embodiments, the treated PCD table 340 shown in FIG. 3D may besubstantially free of the at least one interstitial constituent.Residual amounts of one or more leaching by-products generated duringthe removal of the at least one interstitial constituent during theleaching process may still remain in at least some of the interstitialregions of the treated PCD table 340. For example, the one or moreleaching by-products may include salts, such as one or more chlorides ofBe, Mg, Ca, Sr, Ba, Li, Na, and K; one or more fluorides of Be, Mg, Ca,Sr, Ba, Li, Na, and K; or any combination of the foregoing salts. Thespecific type of the one or more salts that may be present in the PCDtable 340 depends upon the composition of the at least one carbonatecatalyst material and the acid used to leach the treated PCD table 340.However, the presence of the residual one or more leaching by-productsis not sufficient to significantly inhibit infiltration of the treatedPCD table 340. In some embodiments, the treated PCD table 340 may becleaned to at least partially remove the leaching by-products from thetreated PCD table 340. For example, U.S. Pat. No. 7,845,438, which isincorporated herein in its entirety by this reference, discloses variouscleaning techniques for at least partially removing leaching by-productsfrom the treated PCD table 340.

In some embodiments, the heat treating and material removal processesmay be repeated, as desired or needed. For example, the PCD table may besubjected to any of the material removal processes disclosed herein,followed by heat treating according to any of the material removalprocess, followed by another one of the disclosed material removalprocesses. In another embodiment, the PCD table may be heat treatedaccording to any of the material removal process, followed by subjectingthe heat treated PCD table to any of the material removal processesdisclosed herein, followed by followed by another one of the disclosedheat treating processes.

Prior to or after the material removal process and/or heat treating (ifapplicable), the PCD table 322 may be shaped, such as by machiningand/or grinding, to selectively tailor the geometry of the PCD table322. For example, a chamfer (not shown) may be machined that extendsbetween two major surfaces of the PCD table 322.

Referring to FIG. 3E, the treated carbonate-catalyzed PCD table 340 maybe placed adjacent to the substrate 108 to form an assembly 350. Theassembly 350 may be subjected to an HPHT process using any of the HPHTconditions and pressure transmitting mediums disclosed herein. In someembodiments, the HPHT conditions may include a pressure that is lowerthan the pressure employed in sintering the PCD table, such as at about4-7 GPa and a temperature of about 850 to about 1600° C. or any HPHTdisclosed herein. In some embodiments, the assembly 350 may be sealed ina can assembly as disclosed in U.S. application Ser. No. 11/545,929,previously incorporated by reference. During the HPHT process, ametallic cementing constituent from the substrate 108 liquefies andinfiltrates as a metallic infiltrant into at least a portion of theinterstitial regions of the bonding region 314 adjacent to the surface309 of the treated carbonate-catalyzed PCD table 340. For example, whenthe substrate 108 is a cobalt-cemented tungsten carbide substrate, themetallic infiltrant may be cobalt provided from a cobalt-cementedtungsten carbide substrate. Upon cooling from the HPHT process, themetallic infiltrant provides a strong metallurgical bond between theinfiltrated carbonate-catalyzed PCD table 340 and the substrate 108,forming the PDC 100 as shown in FIGS. 1A and 3F. Depending upon theextent of the infiltration of the metallic infiltrant, the metallicinfiltrant may infiltrate into a portion of the first region 112adjacent to the at least one lateral surface 107.

In other embodiments, the PCD table 322 or 322′ may be placed adjacentto the substrate 108 to form an assembly. The assembly may be subjectedto an HPHT process using any of the HPHT conditions and pressuretransmitting mediums disclosed herein. In such an embodiment, the PCDtable 322 or 322′ may be heat treated and/or subjected to a materialremoval process according to any of the techniques disclosed hereinprior to and/or after bonding to the substrate 108, if desired. Aspreviously described, during the HPHT process, a metallic cementingconstituent from the substrate 108 liquefies and infiltrates as ametallic infiltrant into at least a portion of the high concentration ofinterstitial regions of the bonding region 314 adjacent to the backsurface 306 of the PCD table 322 or 322′. In yet another embodiment, thePCD table 322/322′ or 340 may be brazed to the substrate in a vacuumfurnace using any of the braze alloys disclosed herein prior to and/orafter being subjected to any of the heat treatments and/or materialremoval processes disclosed herein.

The following Working Examples 1-8 of the invention set forth variousembodiments for fabricating magnesium-carbonate-catalyzed PCD tables andbonding magnesium-carbonate-catalyzed PCD tables to cobalt-cementedtungsten carbide substrates. The following working examples providefurther detail in connection with the specific embodiments describedabove.

Working Example 1

A magnesium-carbonate-catalyzed PCD table was initially fabricated bydisposing a magnesium carbonate catalyst material between two regions,each of which included a plurality of synthetic diamond particles havingan average diamond particle size of about 20 μm to form an assembly. Theassembly was subjected to an HPHT process at a temperature of about2200° C. and a cell pressure of about 7.7 GPa in a cubic press to form acarbonate-catalyzed PCD precursor assembly similar to that shown inFIGS. 3A-3C. Two magnesium-carbonate-catalyzed PCD tables weresubsequently separated from the carbonate-catalyzed PCD precursorassembly. Each of the magnesium-carbonate-catalyzed PCD tables exhibiteda gradient of interstitial porosity concentration exhibiting increasedporosity in a bonding region thereof, as shown in FIG. 3C.

The magnesium-carbonate-catalyzed PCD table was subjected to a leachingprocess by immersing the carbonate-catalyzed PCD table in a 50% vol/volsolution of acetic acid at approximately 118° C. for 2 hours topartially remove the magnesium-based interstitial constituent (e.g., MgOand/or MgCO₃) within the interstitial regions between the bonded diamondgrains of the magnesium-carbonate-catalyzed PCD table. Themagnesium-carbonate-catalyzed PCD table was then immersed in boilingdeionized water for 2 hours. Following the treating themagnesium-carbonate-catalyzed PCD table in the boiling deionized water,the magnesium-carbonate-catalyzed PCD table was heat treated at about1200° C. for about 1 hour in a vacuum furnace to at least partiallyconvert magnesium carbonate in the magnesium-carbonate-catalyzed PCDtable to magnesium oxide, while releasing gaseous by-products such as,for example, carbon dioxide and/or carbon monoxide.

After heat treating, the magnesium-carbonate-catalyzed PCD table wasbrazed to a cobalt-cemented tungsten carbide substrate using two foilsof Copper ABA™ braze alloy. The Copper ABA™ braze alloy had acomposition of about 92.75 weight % copper, about 3.0 weight % silicon,about 2.25 weight % titanium, and 2.0 weight % aluminum. Each foil had athickness of about 0.0020 inch. The two foils were placed between thecobalt-cemented tungsten carbide substrate and the high porosity regionof the magnesium-carbonate-catalyzed PCD table. Themagnesium-carbonate-catalyzed PCD table was brazed to thecobalt-cemented tungsten carbide substrate under partial vacuumconditions.

Working Example 2

A magnesium-carbonate-catalyzed PCD table was fabricated as described inWorking Example 1 and heat treated at about 1200° C. for a period ofabout one hour in a vacuum furnace to at least partially convertmagnesium carbonate formed within interstitial regions of themagnesium-carbonate-catalyzed PCD table to magnesium oxide. Followingthe heat treatment, the magnesium-carbonate-catalyzed PCD table wasboiled in a 50% vol/vol of acetic acid solution at about 118° C. for 2hours to at least partially remove the magnesium-based interstitialconstituent (e.g., MgO and/or MgCO₃) within the interstitial regionsbetween the bonded diamond grains of the magnesium-carbonate-catalyzedPCD table. The magnesium-carbonate-catalyzed PCD table was subsequentlyimmersed in boiling deionized water for 2 hours.

After being immersed in boiling deionized water, themagnesium-carbonate-catalyzed PCD table was brazed to a cobalt-cementedtungsten carbide substrate using two foils of Copper ABA™ braze alloy.The two foils were placed between the cobalt-cemented tungsten carbidesubstrate and the high porosity region of themagnesium-carbonate-catalyzed PCD table. Each foil had a thickness ofabout 0.0020 inch. The brazing process was carried out under the sameconditions as performed in Working Example 1.

Working Example 3

A magnesium-carbonate-catalyzed PCD table was fabricated as described inWorking Example 1 and subjected to a leaching process in a solution ofhydrofluoric acid and nitric acid for 8 hours to at least partiallyremove the magnesium-based interstitial constituent (e.g., MgO and/orMgCO₃) within the interstitial regions between the bonded diamond grainsof the carbonate-catalyzed PCD table. After leaching, themagnesium-carbonate-catalyzed PCD table was brazed to a cobalt-cementedtungsten carbide substrate using two foils of Copper ABA™ braze alloy.The two foils were placed between the cobalt-cemented tungsten carbidesubstrate and the high porosity region of themagnesium-carbonate-catalyzed PCD table (i.e., bonding region 314 inFIG. 3C). Each foil had a thickness of about 0.0020 inch. The brazingprocess was carried out under the same conditions as performed inWorking Example 1.

FIG. 4A shows a graph of data for magnesium content in one of themagnesium-carbonate-catalyzed PCD tables from each of Working Examples1-3 prior to being bonded to the cobalt-cemented tungsten carbidesubstrate. The magnesium content was measured using EDS in a SEM. Asshown in FIG. 4A, magnesium content increases within themagnesium-carbonate-catalyzed PCD table with increasing distance fromthe bonding regions 314 (left side of graph) to the first regions 312(right side of graph) (see FIG. 3C).

Working Example 4

A magnesium-carbonate-catalyzed PCD table was fabricated as described inWorking Example 1 and heat treated at about 1150° C. in a vacuum furnaceto at least partially decompose the MgCO₃ to magnesium oxide. After heattreating, the magnesium-carbonate-catalyzed PCD table was brazed to acobalt-cemented tungsten carbide substrate using two foils of CopperABA™ under diamond-stable conditions in a cubic press at a temperatureof about 1050° C. The two foils were placed between the cobalt-cementedtungsten carbide substrate and the high porosity region of themagnesium-carbonate-catalyzed PCD table. Each foil had a thickness ofabout 0.0020 inch.

FIG. 4B is a graph of data showing the metal content within the finalmagnesium-carbonate-catalyzed PCD table of Working Example 4 followingthe brazing process relative to distance from the bottom surface of thecobalt-cemented tungsten carbide substrate. As shown in FIG. 4B that themetal content from both the magnesium catalyst and the braze alloy inthe magnesium-carbonate-catalyzed PCD table decreased with distance fromthe cobalt-cemented tungsten carbide substrate as is consistent with thedecreasing gradient in interstitial porosity concentration of themagnesium-carbonate-catalyzed PCD table from the bonding region to theworking surface.

Working Example 5

A magnesium-carbonate-catalyzed PCD table was fabricated as described inWorking Example 1 and heat treated at about 1200° C. for about 30minutes in a vacuum furnace to at least partially convert magnesiumcarbonate in interstitial regions of the magnesium-carbonate-catalyzedPCD table to magnesium oxide, thereby releasing gaseous by-products(e.g., carbon monoxide and/or carbon dioxide). Following heat treatment,the magnesium-carbonate-catalyzed PCD table was assembled with acobalt-cemented tungsten carbide substrate to form an assembly, with thehigher porosity region of the magnesium-carbonate-catalyzed PCD tableplaced adjacent to the cobalt-cemented tungsten carbide substrate. Theassembly was subjected to an HPHT process at a temperature of about1400° C. and a cell pressure of about 5.5 GPa using a cubic press inorder to bond the magnesium-carbonate-catalyzed PCD table placedadjacent to the cobalt-cemented tungsten carbide substrate. During theHPHT process, cobalt from the cobalt-cemented tungsten carbide substratemelted and infiltrated into the magnesium-carbonate-catalyzed PCD tableso that the magnesium-carbonate-catalyzed PCD table was effectivelybonded to the cobalt-cemented tungsten carbide substrate.

Working Example 6

A magnesium-carbonate-catalyzed PCD table was fabricated as described inWorking Example 1 and heat treated at about 1200° C. for about 30minutes in a vacuum furnace to at least partially convert magnesiumcarbonate in interstitial regions of the magnesium-carbonate-catalyzedPCD table to magnesium oxide, thereby releasing gaseous by-products(e.g., carbon monoxide and/or carbon dioxide). As previously discussed,the release of such gases may facilitate the infiltration of cobalt intothe interstitial regions between the diamond grains in themagnesium-carbonate-catalyzed PCD table. Following the heat treatment,the magnesium-carbonate-catalyzed PCD table was immersed in hydrochloricacid maintained at about 75° C. for about 72 hours to at least partiallyremove the interstitial constituent (e.g., magnesium oxide and/ormagnesium carbonate) within the interstitial regions between the diamondgrains of the magnesium-carbonate-catalyzed PCD table. Themagnesium-carbonate-catalyzed PCD table was subsequently subjected to asecond heat treatment at about 1200° C. for about 30 minutes. After thesecond heat treatment, the magnesium-carbonate-catalyzed PCD table wasattached to a cobalt-cemented tungsten carbide substrate as performed inWorking Example 5.

Following the HPHT bonding of the magnesium-carbonate-catalyzed PCDtables, the metal content profile in the magnesium-carbonate-catalyzedPCD tables of the PDCs of Working Examples 5 and 6 were analyzed usingEDS in a SEM. The results of the analysis of thesemagnesium-carbonate-catalyzed PCD tables are shown in FIG. 5.

FIG. 5 is a scatter plot of data illustrating the magnesium and cobaltcontent measured in the magnesium-carbonate-catalyzed PCD tables of PDCsof Working Examples 5 and 6. The plot shown in FIG. 5, illustrates ahigher concentration of cobalt in the bonding region closest to thecobalt-cemented tungsten carbide substrate, with a substantially reducedamount of cobalt in the region (near the working surface) of themagnesium-carbonate-catalyzed PCD table farthest from thecobalt-cemented tungsten carbide substrate. Magnesium generallyincreases and cobalt generally decreases with distance from thecobalt-cemented tungsten carbide substrate. This observation isconsistent with the higher interstitial porosity concentration of thebonding region adjacent to the cobalt-cemented tungsten carbidesubstrate that facilitated a relatively higher amount of cobaltinfiltration during the HPHT bonding process compared to the lowerinterstitial porosity concentration of the region near the workingsurface. FIG. 5 also illustrates the increase in the amount of magnesiumin the region of the magnesium-carbonate-catalyzed PCD table (near theworking surface) compared to the bonding region closer to thecobalt-cemented tungsten carbide substrate.

Working Example 7

A magnesium-carbonate-catalyzed PCD table was fabricated as described inWorking Example 1. The magnesium-carbonate-catalyzed PCD table wasstructured similarly to the PCD table 322 having a bonding region 314and a region 312 shown in FIG. 3. The magnesium-carbonate-catalyzed PCDtable was analyzed by Rietveld XRD analysis to determine the compositionof the bonding region 314 and the first region. Unlike Working Examples4-6, the magnesium-carbonate-catalyzed PCD table analyzed wasfreestanding (i.e., not bonded to a substrate). The Rietveld analysisdemonstrated that the concentration of magnesium carbonate at and/ornear a surface 309/309′ of the bonding region 314/314′ was about 0.7weight % and the concentration of magnesium carbonate at and/or near asurface 307/307′ of the region 312 was about 2.1 weight %.

Working Example 8

Synthetic diamond powder having an average particle size of about 20 μmfrom Engis Corporation U.S.A and natural magnesium carbonate powderhaving an average particle size of about 7 μm from Causmag InternationalAustralia were used as starting materials. The diamond powders werelayered beneath and above the magnesium carbonate as shown in FIG. 3A.Layered diamond and magnesium carbonate powders were encapsulated insidetantalum foil to prevent contamination from molten salt of the cellassembly during HPHT sintering.

The diamond powders layered beneath and above the magnesium carbonateenclosed in the tantalum foil were HPHT sintered at around 8 GPa cellpressure and 2200-2400° C. for 5 minutes in a cubic press. Internalpressure was calibrated with fixed pressure points from bismuth (I-II2.5 GPa, II-III 2.7 GPa, III-V 7.7 GPa), tellurium (I-II 4.0 GPa), andlead telluride (6.0 GPa). Temperature was either directly measured withW5% Re-W26% Re thermocouples or estimated from electric heatingpower-temperature curves. The pressure effect on thermocouple e.m.f. wasnot corrected. The magnesium-carbonate-catalyzed PCD samples were firstfinished as magnesium-carbonate-catalyzed PCD tables having a diameterof 11 mm and a thickness of 2 mm.

XRD indicated that the MgCO₃ was preserved even after HPHT sintering. Asshown in the backscattered electron SEM image in FIG. 6A of one of themagnesium-carbonate-catalyzed PCD tables of Working Example 8, themagnesium-carbonate-catalyzed PCD table exhibited a substantiallyhomogeneous sintered dense microstructure having intergranular diamondgrowth. Though the Z numbers of carbon, oxygen, and magnesium are close,darker black/gray diamond grains are differentiable from white, lighterMgCO₃ areas. No abnormal diamond grain growth was visible.

Each magnesium-carbonate-catalyzed PCD table was brazed to acobalt-cemented tungsten carbide substrate in a vacuum furnace at about800-850° C. using a TICUSIL® braze alloy foil having a composition ofabout 4.5 weight % titanium, about 26.7 weight % copper, and about 68.8weight % silver to form a PDC. The magnesium-carbonate-catalyzed PCDtable was assembled with the cobalt-cemented tungsten carbide substrateso that the high porosity region of the PCD disc was placed adjacent tothe cobalt-cemented tungsten carbide substrate.

The wear resistance of the PDCs were measured by cutting granite with awater-based coolant on a vertical turret lathe (“VTL”). Thermalstability was measured on the same VTL test, but without coolant.Cutting parameters the wear resistance test are a depth of cut for thePDC of about 0.254 mm, a back rake angle for the PDC of about 20degrees, an in-feed for the PDC of about 6.35 mm/rev, and a rotary speedof the workpiece to be cut of about 101 rpm. The workpiece was cooledwith a coolant. Cutting parameters for the thermal stability test was adepth of cut for the PDC of about 1.27 mm, a back rake angle for the PDCof about 20 degrees, an in-feed for the PDC of about 1.524 mm/rev, acutting speed of the workpiece to be cut of about 1.78 m/sec.

Rupture strength was measured on 1 mm thick PDC discs using a burst discapparatus. The thin discs of the PDCs were supported along the outerdiameter, and hydraulic pressure was applied to one side of the PDC discuntil it ruptured. The maximum stress was calculated from the pressureat failure and reported as the rupture strength.

FIGS. 6B-6E contains typical photographs of wear scars on one of thePDCs of Working Example 8 and a conventional cobalt-sintered PDC aftercutting 7,700 cm³ and 15,400 cm³ of granite. The PCD table of thecobalt-sintered PDC samples had a leach depth of about 210 μm. As shownin FIG. 6B, wear barely passes the chamfer with a small half-circle chipon the outer diameter of the PDC of Working Example 8. The wear appearsnarrow in width, but passes beyond the chamfer and reaches the bottomhalf of the PCD table for cobalt-sintered PDC after removing 7,700 cm³of rock, as shown in FIG. 6D. The difference in wear volume becomes morevisible after 15,400 cm³ of rock was removed. The wear surface appearsrough with a chip on the top of the PCD table, but it only extendsapproximately ⅔ of the PCD table for the PDC of Working Example 8 inFIG. 6C. A large, smooth wear scar extends past the WC—Co substrate forcobalt-sintered PDC in FIG. 6E.

FIG. 6F is a statistical comparison of wear volumes between PDCs ofWorking Example 8 and the cobalt-sintered PDCs after removing 15,400 cm³of rock on the wet VTL test. The mean wear volumes were 0.0011 and0.0019 cm³, respectively. A hypothesis test shows that the two meanswere significantly different (p=0.02). Overall, the PDCs of WorkingExample 8 have a better wear resistance than cobalt-sintered PDC due tothe high thermal stability and inert chemical nature of the magnesiumcarbonate catalyst. However, wear scars of the PDCs of Working Example 8may involve slightly more chipping.

On the dry VTL test, the PDCs of Working Example 8 exceeds thecobalt-sintered PDC in thermal stability. In this test, the PDCs ofWorking Example 8 cut against granite without water-based coolant untilthey fail catastrophically. A sudden jump in temperature when the PDCfails can be monitored and used to determine the linear distance tofailure. FIG. 6G is a statistical comparison of thermal stabilitybetween the PDCs of Working Example 8 and the cobalt-sintered PDCs. Themean distance to failure was 6300 and 1440 meters, respectively. Ahypothesis tests shows the two means were significantly different(p=0.01), which can be seen by the clear separation of the twoconfidence interval circles on the student's t plot in FIG. 6G. Theexceptional thermal stability of the PDCs of Working Example 8 wasbelieved to be derived from the presence of interstitial magnesiumcarbonate among the bonded diamond grains.

Rupture strength is another property of superhard materials, and it ishypothesized to decrease when the tested materials change from ductileto brittle. FIG. 6H is the statistical comparison of rupture strengthbetween WC-13 weight % Co disc, the cobalt-sintered PDC discs, and thePDCs of Working Example 8. The mean rupture strengths were 1855, 1208,and 1589 MPa, respectively. A hypothesis test showed that the rupturestrength of the PDCs of Working Example 8 was slightly weaker than WC—Codisc (p=0.25), but was greater than the cobalt-sintered PDC (p=0.03). Aclear gap was observed between the two confidence interval circlesrepresenting the PDCs of Working Example 8 and the cobalt-sintered PDCin FIG. 6H. It was surprising and unexpected that the PDCs of WorkingExample 8 had higher rupture strengths than the cobalt-sintered PDCsbecause both diamond and magnesium carbonate are non-metallic brittlematerials. However, considering the sintering pressure and temperatureof ˜8 GPa/2300° C. and the possible additional carbon from magnesiumcarbonate itself during HPHT sintering, the inventors currently believethat molten magnesium carbonate may dissolve more carbon atoms andfacilitate more diamond precipitation, thereby growing stronger diamondbonds than in the cobalt-sintered PDCs that are sintered atapproximately 6 GPa at a temperature of about 1400° C.

FIGS. 7A and 7B are isometric and top elevation views, respectively, ofa rotary drill bit 700 according to an embodiment. The rotary drill bit700 includes at least one PDC cutting element configured according toany of the previously described leached PDC embodiments. The rotarydrill bit 700 comprises a bit body 702 that includes radially andlongitudinally extending blades 704 with leading faces 706, and athreaded pin connection 708 for connecting the bit body 702 to adrilling string. The bit body 702 defines a leading end structureconfigured for drilling into a subterranean formation by rotation abouta longitudinal axis 710 and application of weight-on-bit. At least onePDC cutting element, manufactured and configured according to any of thepreviously described PDC embodiments, may be affixed to rotary drill bit700 by, for example, brazing, mechanical affixing, or another suitabletechnique. With reference to FIG. 7B, each of a plurality of PDCs 712 issecured to the blades 704. For example, each PDC 712 may include a PCDtable 714 bonded to a substrate 716. More generally, the PDCs 712 maycomprise any PDC disclosed herein, without limitation. In addition, ifdesired, in an embodiment, a number of the PDCs 712 may be conventionalin construction. Also, circumferentially adjacent blades 704 defineso-called junk slots 718 therebetween, as known in the art.Additionally, the rotary drill bit 700 includes a plurality of nozzlecavities 720 for communicating drilling fluid from the interior of therotary drill bit 700 to the PDCs 712.

FIGS. 7A and 7B merely depict one embodiment of a rotary drill bit thatemploys at least one PDC fabricated and structured in accordance withthe disclosed embodiments, without limitation. The rotary drill bit 700is used to represent any number of earth-boring tools or drilling tools,including, for example, core bits, roller-cone bits, fixed-cutter bits,eccentric bits, bicenter bits, reamers, reamer wings, or any otherdownhole tool including superabrasive compacts, without limitation.

For example, FIGS. 8 and 9 disclose embodiments of thrust-bearing andradial bearing apparatuses, respectively. FIG. 8 is an isometriccut-away view of an embodiment of the thrust-bearing apparatus 800,which may utilize any of the disclosed PDC embodiments as bearingelements. The thrust-bearing apparatus 800 includes respectivethrust-bearing assemblies 802. Each thrust-bearing assembly 802 includesan annular support ring 804 that may be fabricated from a material, suchas carbon steel, stainless steel, or another suitable material. Eachsupport ring 804 includes a plurality of recesses (not labeled) thatreceive a corresponding bearing element 806. Each bearing element 806may be mounted to a corresponding support ring 804 within acorresponding recess by brazing, press-fitting, using fasteners, oranother suitable mounting technique. One or more, or all of bearingelements 806 may be configured according to any of the disclosed PDCembodiments. For example, each bearing element 806 may include asubstrate 808 and a PCD table 810, with the PCD table 810 including abearing surface 812.

In use, the bearing surfaces 812 of one of the thrust-bearing assemblies802 bear against the opposing bearing surfaces 812 of the other one ofthe bearing assemblies 802. For example, one of the thrust-bearingassemblies 802 may be operably coupled to a shaft to rotate therewithand may be termed a “rotor.” The other one of the thrust-bearingassemblies 802 may be held stationary and may be termed a “stator.”

FIG. 9 is an isometric cut-away view of an embodiment of a radialbearing apparatus 900, which may utilize any of the disclosed PDCembodiments as bearing elements. The radial bearing apparatus 900includes an inner race 902 positioned generally within an outer race904. The outer race 904 includes a plurality of bearing elements 910affixed thereto that have respective bearing surfaces 912. The innerrace 902 also includes a plurality of bearing elements 906 affixedthereto that have respective bearing surfaces 908. One or more, or allof the bearing elements 906 and 910 may be configured according to anyof the PDC embodiments disclosed herein. The inner race 902 ispositioned generally within the outer race 904, and thus the inner race902 and outer race 904 may be configured so that the bearing surfaces908 and 912 may at least partially contact one another and move relativeto each other as the inner race 902 and outer race 904 rotate relativeto each other during use.

The radial bearing apparatus 900 may be employed in a variety ofmechanical applications. For example, so-called “roller-cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 902 may be mounted to a spindle of aroller cone and the outer race 904 may be mounted to an inner boreformed within a cone and such an outer race 904 and inner race 902 maybe assembled to form a radial bearing apparatus.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall be open ended and have the samemeaning as the word “comprising” and variants thereof (e.g., “comprise”and “comprises”).

What is claimed is:
 1. A polycrystalline diamond element, comprising: abody including a plurality of bonded diamond grains at least partiallydefining a plurality of interstitial regions, an upper surface, a backsurface, and at least one lateral surface extending between the uppersurface and the back surface, the body including: a first regionextending inwardly from the upper surface and the at least one lateralsurface, the first region exhibiting a first interstitial regionconcentration and including at least one interstitial constituentdisposed in at least a portion of the plurality of interstitial regionsof the first region, the at least one interstitial constituent includingone or more of at least one metal carbonate or at least one metal oxide;and a second region extending inwardly from the back surface, the secondregion exhibiting a second interstitial region concentration that isgreater than the first interstitial region concentration.
 2. Thepolycrystalline diamond element of claim 1 wherein the at least oneinterstitial constituent is present at the upper surface of thepolycrystalline diamond element in an amount of greater than 0 weight %to about 5 weight %.
 3. The polycrystalline diamond element of claim 1wherein the at least one interstitial constituent is present at the backsurface of the polycrystalline diamond element in an amount of greaterthan 0 weight % to about 1.5 weight %.
 4. The polycrystalline diamondelement of claim 1 wherein the second interstitial region concentrationis about 1.2 to about 1.5 times the first interstitial regionconcentration.
 5. The polycrystalline diamond element of claim 1 whereinthe second interstitial region concentration is about 2 to about 4 timesthe first interstitial region concentration.
 6. The polycrystallinediamond element of claim 1 wherein the body exhibits a gradient ofinterstitial region concentration that increases from the first regiontoward the second region.
 7. The polycrystalline diamond element ofclaim 1 wherein the plurality of bonded diamond grains exhibits asubstantially uniform average diamond grain size.
 8. The polycrystallinediamond element of claim 1 wherein: the at least one metal carbonateincludes one or more alkali metal carbonates, one or more alkaline earthmetal carbonates, or combinations thereof; and the at least one metaloxide includes one or more alkali metal oxides, one or more alkalineearth metal oxides, or combinations thereof.
 9. A method ofmanufacturing at least one polycrystalline diamond element, the methodcomprising: disposing a plurality of diamond particles adjacent to atleast one carbonate catalyst material; and sintering the plurality ofdiamond particles in the presence of the at least one carbonate catalystmaterial in a high-pressure high-temperature process effective to formthe at least one polycrystalline diamond element, the at least onepolycrystalline diamond element including: a body including a pluralityof bonded diamond grains at least partially defining a plurality ofinterstitial regions, an upper surface, a back surface, and at least onelateral surface extending between the upper surface and the backsurface, the body including: a first region extending inwardly from theupper surface and the at least one lateral surface, the first regionexhibiting a first interstitial region concentration and including atleast one interstitial constituent disposed in at least a portion of theplurality of interstitial regions of the first region, the at least oneinterstitial constituent including the one or more of at least one metalcarbonate or at least one metal oxide; and a second region extendinginwardly from the back surface, the second region exhibiting a secondinterstitial region concentration that is greater than the firstinterstitial region concentration.
 10. The method of claim 9 wherein:the at least one metal carbonate includes one or more alkali metalcarbonates, one or more alkaline earth metal carbonates, or combinationsthereof; and the at least one metal oxide includes one or more alkalimetal oxides, one or more alkaline earth metal oxides, or combinationsthereof.
 11. The method of claim 9 wherein the at least one interstitialconstituent is present at the upper surface of the at least onepolycrystalline diamond element in an amount of greater than 0 to about5 weight %.
 12. The method of claim 9 wherein the at least oneinterstitial constituent is present at the back surface of the at leastone polycrystalline diamond element in an amount of greater than 0 toabout 1.5 weight %.
 13. The method of claim 9 wherein the secondinterstitial region concentration is about 1.2 to about 1.5 times thefirst interstitial region concentration.
 14. The method of claim 13,further comprising infiltrating at least a portion of the plurality ofinterstitial regions of the second region of the at least onepolycrystalline diamond element with a metallic infiltrant, wherein themetallic infiltrant includes one or more of a braze alloy, cobalt, iron,nickel, or alloys of at least one of cobalt, iron, or nickel.
 15. Themethod of claim 14, prior to infiltrating at least a portion of theplurality of interstitial regions of the second region, heat treatingthe at least one polycrystalline diamond element to at least partiallyconvert at least some of the at least one metal carbonate to the atleast one metal oxide.
 16. The method of claim 9 wherein: disposing aplurality of diamond particles adjacent to at least one carbonatecatalyst material includes disposing the at least one carbonate catalystmaterial between a first plurality of diamond particles and a secondplurality of diamond particles to form an assembly; and sintering aplurality of diamond particles in the presence of the at least onecarbonate catalyst material in a high-pressure/high-temperature processincludes subjecting the assembly to high-pressure/high-temperatureprocessing effective to infiltrate the first and second plurality ofdiamond particles with respective portions of the at least one carbonatecatalyst material and form corresponding first and secondpolycrystalline diamond elements.
 17. The method of claim 9, furthercomprising leaching at least a portion of the body of the at least onepolycrystalline diamond element.
 18. A rotary drill bit, comprising: abit body configured to engage a subterranean formation; and a pluralityof polycrystalline diamond cutting elements affixed to the bit body, atleast one of the plurality of polycrystalline diamond cutting elementsincluding: a body including a plurality of bonded diamond grains atleast partially defining a plurality of interstitial regions, an uppersurface, a back surface, and at least one lateral surface extendingbetween the upper surface and the back surface, the body including: afirst region extending inwardly from the upper surface and the at leastone lateral surface, the first region exhibiting a first interstitialregion concentration and including at least one interstitial constituentdisposed in at least a portion of the plurality of interstitial regionsof the first region, the at least one interstitial constituent includingone or more of at least one metal carbonate or at least one metal oxide;and a second region extending inwardly from the back surface, the secondregion exhibiting a second interstitial region concentration that isgreater than the first interstitial region concentration.
 19. The rotarydrill bit of claim 18 wherein the at least one interstitial constituentis present at the upper surface of the at least one of the plurality ofpolycrystalline diamond cutting elements in an amount of greater than 0weight % to about 5 weight %, and wherein the at least one interstitialconstituent is present at the back surface of the at least one of theplurality of polycrystalline diamond cutting elements in an amount ofgreater than 0 weight % to about 1.5 weight %.
 20. The rotary drill bitof claim 18 wherein the second interstitial region concentration isabout 1.2 to about 1.5 times the first interstitial regionconcentration.
 21. The rotary drill bit of claim 18 wherein the secondinterstitial region concentration is about 2 to about 4 times the firstinterstitial region concentration.